Ironing ring having improved lubricating characteristics

Abstract

An ironing ring for use in the manufacture of drawn and ironed unitary sheet metal can bodies made from flat rolled steel blackplate. The interior working surface of the ironing ring is treated by diamond wheel grinding, or the like, to form fine-line indentations which decrease the surface contact of the ironing ring with the metal surface being ironed. The linearly extended indentations extend over the entry portion of the ring to, or into, the dwell portion of the ring and help draw ironing lubricant into the ring during the ironing operation.

What is claimed is: 
     
       1. Improved ironing ring which facilitates ironing of flat rolled steel blackplate container stock in which ironing operation the sidewall of a unitary cup-shaped article is elongated and thinned by passage of the cup-shaped article, while mounted on an ironing mandrel, through an ironing ring concentrically mounted with respect to the ironing mandrel with the central axis of the ironing ring coincident with the longitudinal axis of the ironing mandrel, such ironing ring having a circular interior configuration in a cross-sectional plane which is perpendicular to the central axis of the ironing ring and longitudinal axis of the ironing mandrel during an ironing operation, such longitudinal axis being coincident with the direction of movement of the ironing mandrel,   the ironing ring defining a plurality of surface areas along its interior surface confronting the cylindrical exterior surface of the ironing mandrel mounted cup-shaped article,   such interior surface areas of the ironing ring being symmetrical with respect to the central axis and comprising an entry portion, a dwell portion, and an exit portion confronted in that order during a working stroke of the ironing mandrel,   the entry portion of the ironing ring defining a truncated coincal configuration with its largest diameter in the direction of approach of the ironing mandrel on its working stroke, such entry portion interior surface having an angled relationship with such central axis of about 5° to about 15° at the intersection of such entry portion with a radial plane extending from the central axis of the ironing ring,   the dwell portion of the ironing ring having a substantially cylindrical configuration, such interior surface area of the dwell portion extending longitudinally between the entry portion and the exit portion of the ironing ring,   the exit portion of the ironing ring having a truncated conical configuration with its smallest diameter in the direction of approach of the ironing mandrel on its working stroke,   such exit portion of the ironing ring having an internal surface having an angled relationship with the central axis of less than 5° to prevent binding of sheet metal as the ironing mandrel is driven through the ironing ring, such angled relationship existing at the intersection of such exit portion with a radial plane extending from the central axis of the ironing ring,   such interior surface area of the entry portion of the ironing ring presenting fine-line indentations which act to hold surface lubricant during the working stroke of an ironing operation, such fine-line indentations extending over the surface area of the entry portion contacted by the cup-shaped article during the working stroke and extending toward the dwell portion of the ironing ring, and   such fine-line indentations presenting a center line average of surface irregularities between about 20 and about 50 micro inches.   
     
     
       2. The ironing ring of claim 1 in which such fine-line indentations extend into the dwell portion of the ironing ring. 
     
     
       3. The ironing ring of claim 1 in which the fine-line indentations define a crosshatch helical pattern. 
     
     
       4. The ironing ring of claim 1 in which the fine-line indentations are cut into such entry portion by grinding means having approximately a 100 grit surface.